The present invention relates to the protection of wooden masts, posts or the like, particularly near the transition area or interface region between soil and air whereby particularly the wooden part is equipped with a jacket, and a protective paste is provided between that jacket and the wood portion.
Wooden posts, masts, towers etc. are sometimes used as carrier for cable either power cable, wires or the like or telephone cable. One of the most common uses of wooden posts is of course as door gates, posts for fences or the like. These posts are prepared by a pressure impregnating procedure in other words prior to sinking the lower part of such a post or mast into ground a wood protection medium is forced in the wood under pressure. There remains however a weak point in the mast namely the transition portion between permanently above ground and permanently below ground. This transition between exposure to soil and atmosphere is basically variable. No matter how much protection one provides throughout the post, well above the ground level, mold, fungus, rotting bacteria will sooner or later develop and attack the wood. Usually the life of the subsoil portion as well as of the wooden parts that is well above ground is often several decades, but the particular transition part has a use life of less that 10 years and depending on the soil conditions the life may drop to 5 years or less.
Attempts have been made to treat this transition zone subsequently with materials that contain boron. It was believed that boron compounds act as fungicide. Basically, this is correct however treating the transition with a liquid medium simply fails sooner or later since the applying of the liquid is really impossible owing to the particular low viscosity these liquids happen to have. It has been tried on the other hand to drill holes into the posts, masts or the like, and to insert rods into the bores which rods contain boron. It was hoped that a long lasting diffusion process causes the boron molecules to migrate from these rods into the wood so that in fact rotting is prevented. Again, this is quite correct and effective but on the other hand there is a disadvantage of this method which is a kind of paradox. As stated the soil/atmosphere portion of a post transition is particularly endangered; on the other hand through the drilling of holes one weakens structurally the post or mast right at that endangered portion.
Other attempts to use impregnating material that contain the effective boron really failed because of weather conditions e.g. rain or snow, spray water etc. which leached the boron out of the wood before it could be effective. In a different approach the German printed patent application 20 43 489 proposes a liquid type cover for impregnated wooden masts in order to cover particularly a protective salt layer that has been applied in the transition zone. This protective salt layer is supposed to protect the wooden mast and post against leaching, rain or other humidity e.g. from wet soil. However, it has to be observed that a really good seal is not available. In order to offset the deficiency just outlined, an impregnating container is provided above the cover which gradually, over a long period of time and automatically yields and issues impregnating material. The cover as per the patent application is established through a shrunken hose which is slipped over the mast and then shrunken on the transition zone. Prior to shrinking heat a resisting sealing material will fill all unevennesses, cracks or the like in the foot portion of the mast or post. The upper end of the shrink hose envelops the impregnating container. Between the shrink hose and the wooden mast or post a certain bandage is provided with impregnating salt or protective salt, paste or the like, and through a separate hose the impregnating container replenishes the active material.
It is quite obvious that this particular arrangement is highly labor intensive, particularly as far as installation is concerned. The entire arrangement has to be put into operation when the post or mast is installed. On the other hand the head part of the cover or the head end thereof can be seen only with difficulty so that ultimately in the case of heavy rains the impregnated material is diluted and sooner or later the protecting boron will be leached out of the wood. The impregnating containers are somehow provided for projection from the surface of the post and that inherently makes them prone to mechanical damage. In the case of roads, and if the mast or post is close to road, the projecting impregnating container may easily lead to injuries and is thus undesirable from any point of view.